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【新文速递】2024年1月20日固体力学SCI期刊最新文章

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今日更新:International Journal of Solids and Structures 1 篇,Journal of the Mechanics and Physics of Solids 1 篇,Thin-Walled Structures 5 篇

International Journal of Solids and Structures

Non-contact electromagnetic controlled metamaterial beams for low-frequency vibration suppression

Yu Sun, Haokai Zheng, Qiang Han, Chunlei Li

doi:10.1016/j.ijsolstr.2024.112667

用于低频振动抑制的非接触式电磁控制超材料梁

To address the challenge of suppressing extremely-low frequency vibration and noise in precision instruments and equipment, a novel non-contact metamaterial beams is proposed in this paper. The resonators of the metamaterial beams integrate negative stiffness mechanism and electromagnetic damping tuning system. Based on the magnetic dipole theory and the electromagnetic induction law, the mechanical model of magnetic resonator is established. The band structure and transmission spectrum of the metamaterial beams are obtained by transfer matrix method. Besides, the results of numerical simulations are used to verify the accuracy of theoretical results. The result shows that the negative stiffness can be controlled by nonlinear magnetic force among the magnets. Based on this mechanism, the bandgap frequency can be reduced to a minimum of 50Hz. Then, the method of combining electromagnetic damping and negative impedance circuit is proposed to form a tuning system which can reduce the initial frequency of the bandgap to 4Hz. Interestingly, the proposed bandgap control mechanism achieves the extremely-low bandgap while broadens the bandwith relatively, which overcomes the deficiency of traditional quasi-zero-stiffness metamaterials that reduce the bandgap frequency while causing the bandwidth to narrow. This study is expected to provide valuable ideas for the application of metamaterials in the field of low-frequency vibration and noise reduction.

为解决精密仪器设备中极低频振动和噪声的抑制问题,提出了一种新型非接触式超材料梁。超材料梁谐振腔集成了负刚度机构和电磁阻尼调谐系统。基于磁偶极子理论和电磁感应定律,建立了磁谐振器的力学模型。利用传递矩阵法得到了超材料光束的能带结构和透射谱。此外,用数值模拟结果验证了理论结果的准确性。结果表明,磁体间的非线性磁力可以控制负刚度。基于这种机制,带隙频率可以降低到至少50Hz。然后,提出了电磁阻尼与负阻抗电路相结合的方法,形成了一个可将带隙初始频率降至4Hz的调谐系统。有趣的是,所提出的带隙控制机制实现了极低的带隙,同时相对拓宽了带宽,克服了传统准零刚度超材料在降低带隙频率的同时导致带宽变窄的缺点。该研究有望为超材料在低频振动降噪领域的应用提供有价值的思路。


Journal of the Mechanics and Physics of Solids

Modeling storage particle delamination and electrolyte cracking in cathodes of solid state batteries

Tao Zhang, Marc Kamlah, Robert M. McMeeking

doi:10.1016/j.jmps.2024.105551

固态电池阴极中存储颗粒分层和电解液开裂的模拟

Interface delamination between storage particles and solid electrolytes contributes to greater impedance for Li transfer and capacity loss in solid-state batteries. Electrolyte cracking would cause degradation of the ionic or electronic conductivity of electrolytes. The occurrence of interface delamination and electrolyte cracking is commonly ascribed to mechanical stress, which evolves from inhomogeneous shrinkage and swelling of storage particles confined by the surrounding solid electrolytes when lithium is extracted or inserted. Here, a coupled model of Li diffusion, ionic conduction, interfacial reaction, mechanical stress and a phase field fracture approach is applied to investigate defect-initiated interface delamination and how cracks nucleate in electrolytes in a full 3D dynamical description for the first time. We find that unstable interface delamination is a very likely event during extraction. On the other hand, homogeneous delamination where the whole interface delaminates simultaneously, can happen for smaller interfacial defects with larger particle sizes and higher applied current densities. Larger interfacial defects delay the onset of delamination due to damage dependent interfacial reaction. More particle storage capacity can be utilized for smaller particle sizes and smaller interfacial defects prior to delamination. We further demonstrate electrolyte cracking can happen quite readily, and the electrolyte can break into several parts in only one insertion half cycle and even the appearance of full delamination.

在固态电池中,存储颗粒和固体电解质之间的界面分层导致锂离子转移阻抗增大和容量损失增大。电解液的开裂会导致电解液的离子或电子导电性下降。界面分层和电解质开裂的发生通常归因于机械应力,这是锂提取或插入时由周围固体电解质限制的存储颗粒的不均匀收缩和膨胀演变而来的。本文首次采用Li扩散、离子传导、界面反应、机械应力和相场断裂的耦合模型,对缺陷引发的界面分层以及裂纹如何在电解质中成核进行了完整的三维动力学描述。我们发现不稳定的界面分层是萃取过程中很可能发生的事件。另一方面,对于较小的界面缺陷,较大的颗粒尺寸和较高的施加电流密度,可以发生整个界面同时分层的均匀分层。由于损伤相关的界面反应,较大的界面缺陷延迟了分层的发生。在分层之前,更小的颗粒尺寸和更小的界面缺陷可以利用更多的颗粒存储容量。我们进一步证明了电解质的开裂是很容易发生的,电解质可以在一个插入半周期内分解成几个部分,甚至出现完全分层。


Thin-Walled Structures

Comparison of two progressive damage models for predicting low-velocity impact behavior of woven composites

Yogesh Kumar, Mohammad Rezasefat, Sandro C. Amico, Andrea Manes, Patricia I. Dolez, James D. Hogan

doi:10.1016/j.tws.2024.111611

两种预测编织复合材料低速冲击行为的渐进损伤模型的比较

This research focuses on comparing the two progressive damage models available in the explicit nonlinear finite element software LS-Dyna. To explore the prediction capabilities in terms of mechanical response and dominating failure modes in S2 glass woven composites, low velocity impact response at four different energies ranging from 27.9 J to 109.7 J were considered in this study. A macro-homogeneous solid element formulated finite element model was simulated to understand the response and failure mechanics in the laminate under low-velocity impact. The material modeling was carried out utilizing the MAT 55 and MAT 162 material models. An effort has been made for robust calibration of the various physical and non-physical parameters in both material cards for accurate predictions. The prediction capabilities of the models were then examined by comparing them against the experimental results, which fall within the deviation of ∼ 11%. The results show that MAT 162 yields a better resemblance with the damage morphology patterns and the delamination for the accounted impact zone, due to inclusion of strain-rate effect. Overall, this paper provides insight into the limitations and advantages of both material models, which establishes the route for the selection of the appropriate material model for simulating impact behavior in woven composites.

本文主要对LS-Dyna显式非线性有限元软件中现有的两种渐进损伤模型进行了比较。为了探索S2玻璃编织复合材料力学响应和主要破坏模式的预测能力,本研究考虑了27.9 ~ 109.7 J四种不同能量下的低速冲击响应。为了解层合板在低速冲击下的响应和破坏机理,建立了宏观均质实体有限元模型。利用MAT 55和MAT 162材料模型进行材料建模。为了准确预测,已经努力对两种材料卡中的各种物理和非物理参数进行稳健校准。然后通过将模型与实验结果进行比较来检验模型的预测能力,实验结果的偏差在~ 11%之内。结果表明,由于包含应变率效应,MAT 162与计算的冲击区损伤形态和分层具有更好的相似性。总体而言,本文深入分析了两种材料模型的局限性和优势,为选择合适的材料模型来模拟机织复合材料的冲击行为奠定了基础。


Surface effects on wave propagation in piezoelectric-piezomagnetic loosely bonded bilayer system using nonlocal theory of elasticity

Sudarshan Dhua, Subrata Mondal, Arpita Maji

doi:10.1016/j.tws.2024.111612

基于非局部弹性理论的压电-压电松散键合双层体系中波传播的表面效应

This study investigates nonlocal and surface effects on the dispersion behaviors of Shear horizontal (SH) waves in piezoelectric(PE)- piezomagnetic(PM) bilayer systems. The interface between these two layers is imperfectly bonded. The general governing equations are derived from the nonlocal magnetoelectroelastic (MEE) theory by adding an inherent length. The G-M model and generalized Younge–Laplace equations have been used to incorporate surface effects into the boundary conditions of the bilayer systems. The closed-form dispersion equation is obtained analytically for electrically open and magnetically short conditions. Numerical solutions are utilized to investigate the effects of nonlocal scale parameters and surface parameters on SH surface wave propagation. Contrary to the results of classical theory, the coupling effects of nonlocal small-scale and surface piezoelectricity are more significant than individual effects. Also, it has been observed that the imperfectness parameter across the interface and the thickness ratio of the bilayer significantly affect the phase velocity. Moreover, 2D and 3D plots of the mode shapes of field variables for the propagation of SH waves are presented graphically. These results are validated by conducting analyses excluding nonlocal effects. This allows us to isolate the specific impact of surface effects in the piezoelectric-piezomagnetic bilayer system, drawing connections to existing results and enhancing the robustness of our findings. This study provides valuable insights into complex wave dynamics, helping to optimize the performance and functionality of such smart composites in various engineering applications.

本文研究了压电(PE)-压磁(PM)双层体系中剪切水平波(SH)色散行为的非局域和表面效应。这两层之间的界面是不完美结合的。一般控制方程由非局部磁电弹性(MEE)理论导出,并加入固有长度。利用G-M模型和广义young - laplace方程将表面效应纳入双层系统的边界条件。得到了电开和磁短条件下的闭式色散方程。利用数值解研究了非局部尺度参数和表面参数对SH表面波传播的影响。与经典理论的结果相反,非局部小尺度和表面压电的耦合效应比个体效应更显著。此外,还观察到界面上的缺陷参数和双层膜的厚度比对相速度有显著影响。此外,还给出了SH波传播场变量模态振型的二维和三维图形。通过进行排除非局部效应的分析,验证了这些结果。这使我们能够分离出压电-压电双分子层系统中表面效应的具体影响,将其与现有结果联系起来,并增强我们发现的稳健性。这项研究为复杂的波动动力学提供了有价值的见解,有助于优化这种智能复合材料在各种工程应用中的性能和功能。


GLARE deformation in low-restraint state: tensile and bending behavior

Yao Wang, Xiaokai Ye, Chao Yang, Junzhe Wei, Sifa Zheng, Libin Zhao, Ning Hu

doi:10.1016/j.tws.2024.111613

低约束状态下的眩光变形:拉伸和弯曲行为

Fiber metal laminates (FMLs) possess a better weight reduction effect than traditional metal materials due to the coupling properties of heterogeneous materials, showing promise in the areas of aviation and aerospace. At present, the research on FMLs mainly focuses on the deformation properties after curing while the mechanical properties in the low-restraint state, i.e. the laminates are temporarily not cured and are formed under lower constraint stresses, are not studied in detail. Herein, the low-restraint GLARE is taken as a research object and its deformation characteristics and failure mode are studied using uniaxial tensile, bending experiments and numerical simulation in this paper. Moreover, the influence of key parameters, such as temperature, laminate structure and span length, is investigated, as well as the tensile and bending deformation behavior of GLARE in a low-restraint state is obtained. In addition, based on experimental observations, it is found that the low-restraint GLARE produces the phenomenon of interlayer slip, and the interlaminar residual stress is much smaller than the cured laminate, whereas the deformation limit and performance are improved. This paper provides theoretical bases for the in-depth analysis of deformation properties and forming laws of low-restraint GLARE, guiding further applications of laminates.

由于非均质材料的耦合特性,金属纤维层压板具有比传统金属材料更好的减重效果,在航空航天领域具有广阔的应用前景。目前,对层合材料的研究主要集中在固化后的变形性能上,而对层合材料在低约束状态下,即暂时不固化,在较低约束应力下形成的力学性能研究较少。本文以低约束眩光为研究对象,通过单轴拉伸、弯曲试验和数值模拟对其变形特性和破坏模式进行了研究。此外,研究了温度、层合结构、跨长等关键参数对眩光的影响,得到了眩光在低约束状态下的拉伸和弯曲变形行为。此外,基于实验观察发现,低约束眩光会产生层间滑移现象,层间残余应力远小于固化层板,但变形极限和性能均有所提高。本文为深入分析低约束眩光的变形特性和形成规律提供了理论依据,指导了层合板的进一步应用。


Dual-functional perforated metamaterial plate for amplified energy harvesting of both acoustic and flexural waves

Tian Deng, Luke Zhao, Feng Jin

doi:10.1016/j.tws.2024.111615

双功能穿孔超材料板,用于放大声波和弯曲波的能量收集

Metamaterials with defect states are commonly utilized in energy harvesting from acoustic and elastic waves due to their remarkable ability to localize waves. In this study, a novel piezoelectric energy harvester based on a perforated double-pillars metamaterial plate with a point defect, which offers the advantage of efficiently harvesting both ambient acoustic and flexural wave energy, is proposed. The proposed structure incorporates a locally resonant mechanism that enhances the concentration of vibration energy at the defect band frequency. Then, the amplified wave energy is efficiently converted into electrical energy by attaching a piezoelectric patch at the defect position. To initiate this investigation, the differential quadrature method is employed to theoretically estimate the boundary frequencies of the first band gap. Subsequently, this study investigates how holes size, electrical boundary conditions, and electrical circuit connections affect the energy harvesting of both acoustic and flexural waves. Correspondingly, the mechanisms behind their effects are thoroughly explained. Numerical results demonstrate that the wave energy localization performance can be remarkably amplified with an increasing holes radius, and the harvesters with the 1mm holes radius generate voltages that are approximately 2.12 and 1.44 times higher than those with the 0mm holes radius from acoustic and flexural waves, respectively. Furthermore, variations in the defect band frequency and corresponding wave localization behavior depend on the specific electrical boundary conditions and circuit connection approaches, ultimately leading to distinct results in the output electrical energy. These findings present valuable insights and guidelines for the development of high-performance electronic applications in the context of acoustic and elastic wave energy harvesting.

具有缺陷态的超材料由于其出色的波局部化能力而被广泛应用于声波和弹性波的能量收集中。本文提出了一种基于带点缺陷的多孔双柱超材料板的新型压电能量收集器,该收集器具有有效收集环境声波和弯曲波能量的优点。所提出的结构包含一个局部共振机制,增强了振动能量在缺陷频带频率上的集中。然后,通过在缺陷位置粘贴压电片,将放大后的波能有效地转化为电能。为了开展这项研究,采用微分正交法从理论上估计了第一带隙的边界频率。随后,本研究探讨了孔大小、电边界条件和电路连接如何影响声波和弯曲波的能量收集。相应地,对其作用背后的机制也作了详尽的解释。数值结果表明,随着孔半径的增大,波能局域化性能显著增强,孔半径为1mm的收集器产生的声波电压和弯曲波电压分别比孔半径为0mm的收集器高约2.12倍和1.44倍。此外,缺陷频带频率的变化和相应的波局部化行为取决于特定的电边界条件和电路连接方式,最终导致输出电能的不同结果。这些发现为在声学和弹性波能收集的背景下开发高性能电子应用提供了有价值的见解和指导方针。


Aerodynamic Stability and Free Vibration of FGP-Reinforced Nano-Fillers Annular Sector Microplates Exposed to Supersonic Flow

Ehsan Arshid, Saeed Amir, Abbas Loghman, Ömer Civalek

doi:10.1016/j.tws.2024.111610

超声速流动下fgp增强纳米填料环形扇形微板的气动稳定性和自由振动

Metal foams have many different uses, but they also have some weaknesses. To address this issue, scientists are exploring the possibility of adding nano-fillers to make them stronger and more rigid. As a result, there has been increased interest in analyzing structures that are made from these materials among researchers. Here and now, the authors have conducted a new study that focuses on analyzing the aerodynamic stability and free vibrational characteristics of an annular sector microplate. This is the first time that such an analysis has been done for this type of microplate. The microplate is exposed to supersonic flow and nonlinear temperature changes. The actual properties of the microplate are determined via different introduced homogenization schemes; and four distinguished patterns for both pores and nano-fillers dispersion are considered. To evaluate the reinforcements impact, two most widely recognized nano-fillers, i.e., carbon nanotubes and graphene nanoplatelets are employed and their influence on the outcomes is observed. By utilizing Hamilton's principle and performing certain mathematical operations, the equations of motion were derived and solved numerically under different boundary conditions. A case study is conducted to examine how different parameters affect the natural frequencies, corresponding mode shapes, and critical aerodynamic pressures. Since no similar research has been found, the outcomes of this work may be accounted as reference points for upcoming investigations.

金属泡沫有许多不同的用途,但它们也有一些弱点。为了解决这个问题,科学家们正在探索添加纳米填充物的可能性,以使它们更坚固、更坚硬。因此,研究人员对分析由这些材料制成的结构越来越感兴趣。在此,作者进行了一项新的研究,重点分析了环形扇形微孔板的气动稳定性和自由振动特性。这是第一次对这种类型的微孔板进行这样的分析。微孔板暴露在超声速流动和非线性温度变化中。通过引入不同的均质方案来确定微孔板的实际性能;并考虑了孔隙和纳米填料分散的四种不同模式。为了评估增强剂的影响,采用了两种最广泛认可的纳米填料,即碳纳米管和石墨烯纳米片,并观察了它们对结果的影响。利用哈密顿原理,进行一定的数学运算,推导出不同边界条件下的运动方程,并对其进行数值求解。通过实例分析,研究了不同参数对固有频率、相应模态振型和临界气动压力的影响。由于没有发现类似的研究,这项工作的结果可以作为今后调查的参考点。



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【新文速递】2024年1月5日固体力学SCI期刊最新文章

今日更新:International Journal of Solids and Structures 2 篇,Journal of the Mechanics and Physics of Solids 1 篇,Mechanics of Materials 1 篇,Thin-Walled Structures 2 篇International Journal of Solids and StructuresAnalytical 3D model for coupled magneto-mechanical behaviors of ferromagnetic shape memory alloyQi Peng, Jiahui Chen, Ke Ni, Ze Liu, Long-Qing Chen, Zhengzhi Wangdoi:10.1016/j.ijsolstr.2023.112619铁磁形状记忆合金耦合磁力学行为的三维分析模型Ferromagnetic shape memory alloys (FSMA), a type of smart material, are promising for engineering applications due to their large, high-frequency, and reversible magnetic-field-induced-strain (MFIS). However, the magneto-mechanical behaviors of FSMA are still not well understood due to the intrinsically coupled and cross-scale magneto-mechanical responses, limiting the design and optimization of FSMA-based devices such as sensors and actuators. In this work, a fully-analytical 3D model containing only basic material parameters and incorporating all key mechanisms for the magneto-mechanical performances of FSMA is developed based on a new magneto-mechano-decoupled energy minimization approach. It is shown that the coupled magneto-mechanical responses of FSMA-based sensors (cyclic stress with constant magnetic field) and actuators (cyclic magnetic field with constant stress) predicted by the model are in excellent agreement with existing experimental measurements. Based on these analytical predictions, the optimal ranges for the constant field and demagnetization factor are determined to achieve simultaneous complete strain recovery and considerable magnetization change as required by the FSMA-based sensors. In addition, the dependences of switching and saturating fields of MFIS on the constant stress and demagnetization factor are quantified for the FSMA-based actuators. Finally, a phase diagram is constructed to quantitatively determine the critical magnetic fields and stresses for predicting the strain induction and recovery under various loading conditions. The analytical model provides a simple, reliable, and versatile tool to reveal the comprehensive mechanisms for the coupled magneto-mechanical behaviors of FSMA and to guide the design of FSMA-based sensors and actuators with customized and on-demand performances.铁磁形状记忆合金(FSMA)是一种智能材料,由于其具有大尺寸、高频率和可逆磁场诱导应变(MFIS)的特点,因此在工程应用中大有可为。然而,由于其内在耦合和跨尺度磁力学响应,人们对 FSMA 的磁力学行为仍不甚了解,从而限制了基于 FSMA 的传感器和致动器等设备的设计和优化。在这项工作中,基于一种新的磁-机-解耦能量最小化方法,开发了一种仅包含基本材料参数的全分析三维模型,该模型包含了 FSMA 磁-机械性能的所有关键机制。结果表明,该模型预测的基于 FSMA 的传感器(恒定磁场的循环应力)和致动器(恒定应力的循环磁场)的耦合磁力学响应与现有的实验测量结果非常吻合。根据这些分析预测,确定了恒定磁场和退磁因子的最佳范围,以实现基于 FSMA 的传感器所需的完全应变恢复和显著磁化变化。此外,还量化了基于 FSMA 的致动器的 MFIS 开关场和饱和场对恒定应力和退磁因子的依赖关系。最后,构建了一个相图,以定量确定临界磁场和应力,从而预测各种加载条件下的应变感应和恢复。该分析模型提供了一种简单、可靠和通用的工具,可用于揭示 FSMA 磁力学耦合行为的综合机制,并指导设计具有定制和按需性能的基于 FSMA 的传感器和致动器。Nonlocal interfaces accounting for progressive damage within continuum-kinematics-inspired peridynamicsMarie Laurien, Ali Javili, Paul Steinmanndoi:10.1016/j.ijsolstr.2023.112641非局部界面在连续运动学启发的周动力学中解释渐进损伤In this work, we present a modeling approach to nonlocal material interfaces in the framework of continuum-kinematics-inspired peridynamics. The nonlocal model accounts for progressive damage within a finite-thickness interface, as opposed to the more common practice of abrupt bond breakage across a zero-thickness interface. Our approach is based on an overlap of the constituents within the interface. Interfacial bonds between initially overlapping partner points are governed by a constitutive law reminiscent of a traction-separation-law. The governing equations for continuum-kinematics-inspired peridynamics in the presence of an interface are derived using a rate-variational principle. The damage formulation is established using the classical concept of internal variables. Following the notion of a standard dissipative material, thermodynamic consistency of the constitutive laws and the evolution of the internal variables is ensured. The latter results in a straightforward evaluation of a damage function. We give details about the computational implementation comprising a peridynamic discretization and a Newton–Raphson scheme. A sound approach to approximate the interface normal during deformation is presented, which allows to penalize material penetration across the interface. The proposed model is explored in a series of numerical examples, i.e., classical peeling and shearing tests, for a variety of damage functions. A key feature of our interface model are the nonlocal characteristics that are assumed to play a role especially at small scales. We, first, observe that an increasing thickness of the nonlocal interface leads to stronger interfacial bonding and less damage. Second, an increase in horizon size results in stiffer material behavior. When studying the wrinkling and delamination behavior of a compressed bilayer, it is found that an increase in interface stiffness leads to a smaller wrinkling wavelength. Moreover, delamination due to progressive damage of interfacial bonds in the post-wrinkling regime is observed, which, to the best of our knowledge, has not been studied in a nonlocal model before.在这项工作中,我们在连续介质动力学启发的周动力学框架内提出了一种非局部材料界面建模方法。非局部模型考虑了有限厚度界面内的渐进式损坏,而不是更常见的零厚度界面上的突然断裂。我们的方法基于界面内成分的重叠。最初重叠的伙伴点之间的界面键受类似于牵引分离定律的构成定律支配。在存在界面的情况下,连续介质启发的周动力学控制方程是利用速率变异原理推导出来的。利用经典的内部变量概念建立了损伤公式。根据标准耗散材料的概念,确保了构成定律和内部变量演变的热力学一致性。后者可直接评估损伤函数。我们详细介绍了由周动态离散化和牛顿-拉斐森方案组成的计算实施。我们还介绍了在变形过程中近似界面法线的合理方法,该方法允许对跨界面的材料渗透进行惩罚。在一系列数值示例中,即经典的剥离和剪切试验中,针对各种损伤函数,对所提出的模型进行了探讨。我们的界面模型的一个主要特点是假定非局部特征在小尺度上发挥作用。首先,我们观察到非局部界面厚度的增加会导致更强的界面结合力和更小的损伤。其次,地平线尺寸的增加会导致材料更坚硬。在研究压缩双分子层的起皱和分层行为时,我们发现界面刚度的增加会导致起皱波长变小。此外,我们还观察到了由于界面键在起皱后逐渐损坏而导致的分层现象,据我们所知,这种现象以前从未在非局部模型中进行过研究。Journal of the Mechanics and Physics of SolidsMorphomechanics of growing curled petals and leavesTing Wang, Chenbo Fu, Michel Potier-Ferry, Fan Xudoi:10.1016/j.jmps.2023.105534 卷曲花瓣和叶片生长的形态力学Petals and leaves are usually curled and exhibit intriguing morphology evolution upon growth, which contributes to their important biological functions. To understand the underlying morphoelastic mechanism and to determine the crucial factors that govern the growth-induced instability patterning in curved petals and leaves, we develop an active thin shell model that can describe variable curvatures and spontaneous growth, within the framework of general differential geometry based on curvilinear coordinates and hyperelastic deformation theory. Analytical solutions of distinguished growing shapes such as saddle surface and cylindrical mode are then derived. We reveal distinct morphological evolutions of doubly curved leaves/petals with different curvatures κx (along the main vein) and κy (perpendicular to the main vein) upon differential growth. Compared to the flat (zero curvature) configuration, leaves/petals with longitudinal curvature κx experiences a global bending deformation. With the increase of growth strain, the leaf/petal undergoes a coupling behavior of edge wrinkling and global bending deformation, associated with a pitchfork bifurcation. Conversely, the transverse curvature κy does not lead to significant bending behavior, but results in delayed critical buckling threshold and reduced wrinkling amplitude. Physical insights into curvature effects on morphology evolutions are further provided by the analysis of nonlinear competition between bending and membrane energies. Moreover, we explore the effect of vein constraint on pattern formation, showing that different from edge wrinkling observed in leaves with strong vein constraint, the ones with weak vein constraint are prone to grow into a saddle shape, which is consistent with analytical solutions. The results uncover the intricate interplay between configurational curvature and vein confinement on plant morphogenesis, providing fundamental insights into a variety of growing shapes of curled petals and leaves.花瓣和叶片通常是卷曲的,在生长过程中会出现奇妙的形态演变,这有助于它们发挥重要的生物功能。为了了解其潜在的形态弹性机制,并确定支配弯曲花瓣和叶片生长诱导不稳定形态的关键因素,我们在基于曲线坐标和超弹性变形理论的一般微分几何框架内,建立了一个能描述可变曲率和自发生长的主动薄壳模型。然后推导出不同生长形状(如鞍面和圆柱模式)的解析解。我们揭示了双曲线叶片/花瓣在微分生长过程中不同曲率κx(沿主脉)和κy(垂直于主脉)的独特形态演变。与扁平(零曲率)结构相比,纵向曲率为 κx 的叶片/花瓣会出现整体弯曲变形。随着生长应变的增加,叶片/花瓣会出现边缘起皱和整体弯曲变形的耦合行为,这与干叉形分叉有关。相反,横向曲率 κy 不会导致明显的弯曲行为,但会导致临界屈曲阈值延迟和皱缩幅度减小。通过分析弯曲和膜能之间的非线性竞争,我们进一步了解了曲率对形态演变的物理影响。此外,我们还探讨了叶脉约束对形态形成的影响,结果表明,与在强叶脉约束下观察到的边缘起皱不同,弱叶脉约束下的叶片容易长成马鞍形,这与分析解一致。这些结果揭示了构型曲率和叶脉约束对植物形态发生的复杂相互作用,为研究各种卷曲花瓣和叶片的生长形状提供了基本见解。Mechanics of MaterialsA nonlinear continuum framework for constitutive modeling of active polymer gelsPriyanka Nemani, Ravi Sastri Ayyagari, Pratyush Dayaldoi:10.1016/j.mechmat.2023.104908活性聚合物凝胶构成建模的非线性连续体框架Chemo-mechanical transduction is one of the key mechanisms that has formed the basis for designing bio-inspired self-driven synthetic systems from soft materials. Polymer hydrogels that use Belousov–Zhabotinsky (BZ) reaction are a unique class of dynamical reaction–diffusion (RD) systems that can continuously transduce internal chemical energy, from the reaction, to produce sustained mechanical work. In particular, BZ gels represent a complex nonlinear chemo-mechanical system, wherein, the autocatalytic oscillatory BZ reaction drives the rhythmic mechanical deformations through polymer-solvent interdiffusion. The objective of our work is to develop a standardized finite element (FE) framework for chemically driven active hydrogels that captures nonlinear elastic deformations with limited chain extensibility. The distinguishing feature of our approach is that, unlike other approaches, it combines reaction kinetics, solvent transport, elastodynamics of the polymeric network, and polymer-solvent friction under a unified FE framework. Moreover, we adapt our approach to a specific case of BZ gels and capture its swelling-deswelling characteristics. We first implement our FE framework in MATLAB that subsequently, forms the basis for constructing a three-dimensional user element subroutine (3D-UEL) in ABAQUS. Ultimately, through our simulations, we are able to capture all the essential features of BZ gels that includes chemically driven mechanical deformations. In addition, we also demonstrate that our 3D-UEL efficiently captures the chemo-mechanical response of “stent-shaped” BZ gels–a non-standard 3D geometry. In essence, our FE approach not only allows us to simulate BZ gels but also provides a template for other active, dynamical, RD-based systems, driven by chemo-mechanical transduction, irrespective of internal or external mechanisms.化学机械传导是一种关键机制,是利用软材料设计生物启发自驱动合成系统的基础。使用别洛乌索夫-扎博金斯基(Belousov-Zhabotinsky,BZ)反应的聚合物水凝胶是一类独特的动态反应-扩散(RD)系统,可持续地将反应产生的内部化学能转化为持续的机械功。特别是,BZ 凝胶代表了一种复杂的非线性化学机械系统,其中,自催化振荡 BZ 反应通过聚合物-溶剂相互扩散驱动有节奏的机械变形。我们的工作目标是为化学驱动的活性水凝胶开发一个标准化的有限元(FE)框架,以捕捉具有有限链伸展性的非线性弹性变形。与其他方法不同的是,我们的方法在统一的有限元框架下结合了反应动力学、溶剂传输、聚合物网络弹性动力学以及聚合物-溶剂摩擦。此外,我们还根据 BZ 凝胶的具体情况调整了我们的方法,并捕捉到了其溶胀-消肿特性。我们首先在 MATLAB 中实现了我们的 FE 框架,并在此基础上在 ABAQUS 中构建了三维用户元素子程序(3D-UEL)。最终,通过模拟,我们能够捕捉到 BZ 凝胶的所有基本特征,包括化学驱动的机械变形。此外,我们还证明了我们的 3D-UEL 能够有效捕捉 "支架状 "BZ 凝胶(非标准三维几何形状)的化学机械响应。从本质上讲,我们的 FE 方法不仅能模拟 BZ 凝胶,还能为其他基于 RD 的活性、动态系统提供模板,这些系统由化学机械传导驱动,不受内部或外部机制的影响。Thin-Walled StructuresA Comprehensive Formulation for Determining Static Characteristics of Mosaic Multi-Stable Composite Laminates under Large Deformation and Large RotationM.S. Taki, R. Tikani, S. Ziaei-Raddoi:10.1016/j.tws.2023.111545确定大变形和大旋转下镶嵌式多稳复合层压板静态特性的综合公式Multi-stable composite laminates are composite materials that exhibit multi-stable states, making them highly suitable for use in morphing structures. These materials are capable of maintaining each stable state without expending any energy. As a result, they are used extensively in numerous applications and garnered the interest of scholars and aerospace organizations. In the context of practical applications, such as morphing structures, it is insufficient for designers to rely solely on common bi-stable composite laminates that exhibit large deformations and medium rotations to achieve their desired objectives. Consequently, based on the objectives of the design, there are two potential resolutions to address this limitation. A designer may utilize mosaic multi-stable composite laminates to achieve a morphing structure that exhibits high flexibility, significant deformation, and substantial rotation. The utilization of a series connection between a bi-stable composite laminate and a symmetric composite laminate results in the formation of a mosaic bi-stable composite laminate with variable stiffness. Furthermore, the amalgamation of two asymmetric composite laminates with inverted orientations engenders a mosaic tri-stable composite laminate. The present research examines the static characteristics of mosaic bi-stable and tri-stable composite laminates. It also seeks to analyze the factors affecting the behavior of these types of laminates. A geometrically exact model was formulated for this objective. Apart from the geometrically exact model, a widely used and uncomplicated model relying on the conventional Classical Laminated-Plate Theory (CLPT) and Von-Karman nonlinear strains was employed. The proposed models were validated through finite element simulations. The system's static equations were derived using the virtual work principle and the Rayleigh-Ritz method. The present study examines and explores quasi-static snap-through behavior between stable states through the application of concentrated forces. The findings indicate a high level of concurrence between the outcomes derived from the geometrically exact model and the finite element analyses, particularly in composite laminates exhibiting significant deformations and rotations.多稳定复合层压板是一种呈现多稳定状态的复合材料,因此非常适合用于变形结构。这些材料能够在不消耗任何能量的情况下保持每一种稳定状态。因此,它们被广泛应用于众多领域,并引起了学者和航空航天组织的兴趣。在变形结构等实际应用中,设计人员仅依靠表现出大变形和中等旋转的普通双稳态复合材料层压板来实现预期目标是不够的。因此,根据设计目标,有两种可能的解决方案来解决这一限制。设计者可以利用镶嵌式多稳定复合材料层压板来实现具有高柔性、大变形和大幅度旋转的变形结构。利用双稳态复合材料层压板与对称复合材料层压板之间的串联,可形成刚度可变的镶嵌式双稳态复合材料层压板。此外,将两个方向相反的非对称复合材料层压板组合在一起,还能产生一种镶嵌式三稳复合材料层压板。本研究探讨了马赛克双稳态和三稳态复合层压板的静态特性。研究还试图分析影响这些类型层压板行为的因素。为此,研究人员建立了一个几何精确模型。除几何精确模型外,还采用了一个广泛使用的简单模型,该模型依赖于传统的经典层压板理论(CLPT)和 Von-Karman 非线性应变。通过有限元模拟对所提出的模型进行了验证。系统的静态方程是利用虚功原理和 Rayleigh-Ritz 方法推导出来的。本研究通过施加集中力,检查并探索了稳定状态之间的准静态快速通过行为。研究结果表明,几何精确模型和有限元分析得出的结果高度一致,尤其是在复合材料层压板出现明显变形和旋转时。Experimental investigation on residual capacity of steel-reinforced concrete-filled thin-walled steel tubular columns subjected to combined loading and temperatureWen-Da Wang, Wen-Jing Mao, Kan Zhoudoi:10.1016/j.tws.2024.111557钢筋混凝土填充薄壁钢管柱在荷载和温度共同作用下的残余承载力试验研究Steel-reinforced concrete-filled thin-walled steel tube (SRCFST) is gaining popularity in construction, primarily due to its superior structural performance. However, there is still a scarcity of existing studies examining the residual capacity of SRCFST columns after exposure to fire. Comprehensive research was conducted in this, involving both experimental testing and numerical simulations, to investigate the residual capacity of SRCFST columns. Six SRCFST columns were tested under combined loading and temperature to achieve the temperature distribution, failure modes, residual strength, and structural response within the cross-section. The developed finite element (FE) model was used to validate the test results. Three different paths, including after exposure to fire and without initial load, full-rang fire, and the actual path in the current test, were considered to assess the influence of different time-load-temperature paths on the mechanical properties of SRCFST columns. Results reveal that the region comprised of profiled steel and surrounded concrete forms a composite constraint area, with little loss of strength and stiffness occurring in the core region. The initial load level and heating time ratio were found to have a significant negative influence on the residual load-carrying capacity and ductility of SRCFST columns. By contrast, circular SRCFST columns are more resistant to the effects of fire compared to square SRCFST columns. Finally, the existing design methods were used and extended to evaluate the residual load-carrying capacity of SRCFST columns subjected to a complete temperature-load-time process.钢筋混凝土填充薄壁钢管(SRCFST)在建筑领域越来越受欢迎,这主要归功于其优越的结构性能。然而,目前仍很少有研究探讨 SRCFST 柱在遭受火灾后的剩余承载力。本研究通过实验测试和数值模拟,对 SRCFST 柱的剩余承载力进行了全面研究。对六根 SRCFST 柱进行了综合载荷和温度测试,以了解截面内的温度分布、破坏模式、剩余强度和结构响应。开发的有限元(FE)模型用于验证测试结果。考虑了三种不同的路径,包括暴露于火灾后且无初始荷载、全范围火灾以及本次试验中的实际路径,以评估不同时间-荷载-温度路径对 SRCFST 柱力学性能的影响。结果显示,由型钢和环绕混凝土组成的区域形成了一个复合约束区域,核心区域的强度和刚度损失很小。研究发现,初始荷载水平和加热时间比对 SRCFST 柱的剩余承载能力和延性有显著的负面影响。相比之下,圆形 SRCFST 柱比方形 SRCFST 柱更能抵抗火灾的影响。最后,使用并扩展了现有的设计方法,以评估 SRCFST 柱在完整的温度-荷载-时间过程中的剩余承载能力。来源:复合材料力学仿真Composites FEM

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